The invention relates to a method of controlling a supercharged internal combustion engine having a turbocharger with variable turbine geometry. The engine has a performance graph including a plurality of engine operating points with the corresponding control parameters stored therein for supply to an engine controller and, in addition, turbine control parameters for the turbine.
DE 40 14 398 discloses a control for a turbocharged internal combustion engine whose exhaust gas turbocharger includes an exhaust gas turbine with variable turbine geometry and a charge air compressor. The engine includes a control unit with a load-speed performance graph stored therein, wherein the performance graph is delimited at the top by a full load line and at the bottom by a line for engine driven operation. In order to insure a fast warm-up of a catalytic converter after engine startup, the control unit causes the variable turbine guide vanes to be set to a predetermined position depending on input signals for the coolant temperature, exhaust gas temperature, throttle valve position and engine speed such that the flow cross-section of the exhaust gas duct is reduced during a cold start.
DE 40 25 901 C1 further discloses a method of controlling the charge pressure of an internal combustion engine including an exhaust gas turbocharger with adjustable turbine vanes to a desired charge air pressure depending on engine operating conditions. In this case, the flow cross-section of the turbine guide vanes is reduced and the charge air pressure is controlled first in accordance with a first characteristic line and, after passing a certain threshold value for the exhaust gas pressure in accordance with the first characteristic line. After passing a certain threshold value for the exhaust gas pressure, the charge air pressure is controlled in accordance with a second characteristic line in order to improve the efficiency of the engine during in stationary operation, especially after a positive load change from a low engine load and engine speed.
For general technical background, reference is further made to U.S. Pat. Nos. 4,970,864; 4,779,423 and 4,891,947.
It is the object of the present invention to provide a method of controlling a supercharged internal combustion engine with an exhaust gas turbocharger having a variable turbine geometry. It is also an object of the invention to provide an apparatus for performing the method, wherein the engine control for various engine loads and engine operating states is substantially more variable than is possible with methods and apparatus known in the art.